Hormone

A hormone is a chemical messenger released by a gland or tissue into the bloodstream, which travels and acts on cells elsewhere that carry the matching receptor. The receptor is the important half: a hormone can only affect a cell equipped to hear it, which is why one molecule can do different things in different tissues.

They matter because almost everything this site covers is downstream of hormonal signalling. Insulin directs nutrients into storage, cortisol mobilises energy under stress, thyroid hormones set metabolic pace, testosterone and oestrogen shape tissue, leptin and ghrelin negotiate appetite, and growth hormone and IGF-1 govern growth and repair.

Most run on feedback loops rather than steady levels. The brain senses the output, adjusts the signal, and the system corrects, usually with a daily rhythm layered on top. That is why single measurements are so often uninterpretable: cortisol is high in the morning by design, testosterone swings through the day, and a hormone measured at the wrong hour tells you almost nothing.

The word carries a lot of marketing weight it has not earned. Products promising to balance your hormones rarely name which hormone, in which direction, measured how, and the honest answer is usually that nothing measurable is being changed. Genuine hormonal disorders are diagnosed with repeated testing and treated clinically.

Lifestyle does move them, within limits. Sleep, body composition, alcohol and training load have measurable effects on several of the hormones people care about, and those effects are usually larger than anything sold in a bottle.

Timing and context are part of the result. Cycle phase, fasting state, illness, medication and time of day all change what a number means, which is why direct to consumer hormone panels interpreted without a history are the weakest version of the test.

In practice, treat a single hormone result as a question rather than an answer, and take unexpected ones to a doctor rather than to a supplement.